Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks (PANs) with high levels of security. Bluetooth uses a radio technology called frequency-hopping spread spectrum, which divides the data being sent and transmits portions of it on up to 79 bands (1 MHz each, preferably centered from 2402 to 2480 MHz) in the range 2,400-2,483.5 MHz (allowing for guard bands). This range is in the globally unlicensed Industrial, Scientific and Medical (ISM) 2.4 GHz short-range radio frequency band. Gaussian frequency-shift keying (GFSK) modulation may be used, however, more advanced techniques, such as π/4-DQPSK and 8DPSK modulation may also be used between compatible devices. Devices functioning with GFSK are said to be operating in “basic rate” (BR) mode where an instantaneous data rate of 1 Mbit/s is possible. “Enhanced Data Rate” (EDR) is used to describe π/4-DPSK and 8DPSK schemes, each giving 2 and 3 Mbit/s respectively. The combination of these (BR and EDR) modes in Bluetooth radio technology is classified as a “BR/EDR radio”.
Bluetooth is a packet-based protocol with a master-slave structure. One master may communicate with up to 7 slaves in a piconet, where all devices preferably share the master's clock. Packet exchange is based on the basic clock, defined by the master, which may tick at 312.5 μs intervals. In the simple example of single-slot packets, the master transmits in even slots and receives in odd slots; the slave, conversely, receives in even slots and transmits in odd slots. Packets may be 1, 3 or 5 slots long but in all cases the master transmit will begin in even slots and the slave transmit in odd slots.
Bluetooth provides a secure way to connect and exchange information between devices such as faxes, mobile phones, telephones, laptops, personal computers, printers, Global Positioning System (GPS) receivers, digital cameras, and video game consoles. At any given time, data can be transferred between the master and one other device. The master may choose which slave device to address and may switch rapidly from one device to another in a round-robin fashion. In the area of computer processors, Bluetooth is commonly used to operationally link devices to the computer processor. In other cases, Bluetooth signals are used to “unlock” a computer processor when an enabled device is within a certain proximity.
One area where improvements are needed is in the area of media exposure tracking and web analytics. To date, Bluetooth has been relatively underutilized in this area. What is needed are methods, systems and apparatuses for utilizing Bluetooth signal characteristics in conjunction with media exposure data to produce research data that accurately identifies and characterizes devices, and their accompanying users.